The Virtual Refraction: Useful Spurious Energy in Seismic Interferometry

Dylan Mikesell, Boise State University
Kasper van Wijk, Boise State University
Alexander Calvert, ION-GX Technology
Matt Haney, Boise State University

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Copyright 2009 by the American Geophysical Union. DOI: 10.1190/1.3095659

Abstract

Seismic interferometry is rapidly becoming an established technique to recover the Green’s function between receivers, but practical limitations in the source-energy distribution inevitably lead to spurious energy in the results. Instead of attempting to suppress all such energy, we use a spurious wave associated with the crosscorrelation of refracted energy at both receivers to infer estimates of subsurface parameters. We named this spurious event the virtual refraction. Illustrated by a numerical two-layer example, we found that the slope of the virtual refraction defines the velocity of the faster medium and that the stationary-phase point in the correlation gather provides the critical offset. With the associated critical time derived from the real shot record, this approach includes all of the necessary information to estimate wave speeds and interface depth without the need of inferences from other wave types.